Conventionally, in a sewing operation that sews in a processed fabric using a sewing machine, a sewing machine comprising a threader that can easily perform a threading operation into a needle hole of a sewing needle has been put into practice (see JP 2005-160592A and JP 2002-200386A). For example, in JP 2005-160592A, when an operator lowers a threading lever, a threading shaft and a slider guide shaft are lowered, and the height positions of the threading shaft and the slider guide shaft are regulated when a slider pin at the upper end portion of the threading shaft is brought into contact with a catching portion on the side of a needle bar. Subsequently, when the threading lever is further lowered, the threading shaft comprising the slider pin is rotated by a predetermined angle by a cam mechanism including a slider pin, a hook that is disposed at the lower end portion of the threading shaft is inserted into a needle hole, and then the threading operation is performed.
However, in JP 2005-160592A, it is necessary to manually place a thread over the hook, and, thus, there is a problem in that the operator has to use both hands to perform a threading work. Thus, in JP 2002-200386A, a top thread taken from a bobbin is placed at a predetermined position in the sewing machine and, when the operator lowers the threading lever, the height positions of a threading shaft and a slider guide shaft are regulated when a slider pin at the upper end portion of the threading shaft is brought into contact with a catching portion on the side of a needle bar.
Subsequently, when the threading lever is further lowered, the threading shaft comprising the slider pin is rotated by a predetermined angle by a cam mechanism including the slider pin, and a hook that is disposed at the lower end portion of the threading shaft is inserted into a needle hole. The hook that has been inserted into the needle hole catches the placed top thread, and, when the threading lever is lifted, the threading operation is performed as the hook moves out of the needle hole. In this manner, the operator can perform the threading operation only with an operation that lowers or lifts the threading lever.